Feedstock gel and method of making glass-ceramic articles from the feedstock gel

ABSTRACT

A method of making a glass-ceramic article includes synthesizing a feedstock gel that includes a base oxide network comprising Na 2 O, CaO, and SiO 2 , in which a molar ratio of Na 2 O:CaO:SiO 2  in the gel is 1:2:3, and then converting the feedstock gel into a glass-ceramic article such as a container or a partially-formed container. The conversion of the feedstock gel into a glass-ceramic container may be performed at a temperature that does not exceed 900° C. and may include the steps of pressing the feedstock gel into a compressed solid green-body, sintering the green-body into a solid monolithic body of a glass-ceramic material, deforming the solid monolithic glass-ceramic body into a glass-ceramic preform, and cooling the preform. A glass-ceramic article having a glass-ceramic material that has a molar ratio of Na 2 O:CaO:SiO 2  that is 1:2:3 is also disclosed.

The present disclosure is directed to glass-ceramic articles and methodsof making glass-ceramic articles from a chemically synthesized feedstockgel.

BACKGROUND

Conventional soda-lime-silica glass is a rigid amorphous solid that isused extensively to manufacture a variety of hollow glass articlesincluding containers such as bottles and jars. Soda-lime-silica glasscomprises a disordered and spatially crosslinked ternary oxide networkof Na₂O—CaO—SiO₂, in which the molar ratio of Na₂O:CaO:SiO₂ isapproximately 1:1:6, and may also include other optional oxide andnon-oxide materials, which may be referred to as secondary additives,that act as colorants, decolorants, redox agents, or other agents thataffect the properties the final glass. Some examples of these optionaloxide and non-oxide materials include Al₂O₃, MgO, Li₂O, K₂O, Fe₂O₃,Cr₂O₃, MnO₂, Co₃O₄, TiO₂, SO₃, and selenium. While the exact compositionof the soda-lime-silica glass may be tailored to its particular end-useapplication by the inclusion of secondary additives, the Na₂O—CaO—SiO₂ternary oxide network with its approximately 1:1:6 molar ratio issubject only to minor variances that fall usually within acceptablemanufacturing tolerances.

Soda-lime-silica glass containers are typically produced by a meltprocessing procedure. Generally, during melt processing, a feedstockbatch that includes virgin raw materials and optional recycled glass(i.e., cullet) is first melted in a continuous melting furnace attemperatures in excess of 1400° C. The resultant glass melt ishomogenized and refined—usually downstream of the melting zone of thefurnace—to achieve chemical and thermal consistency and to removebubbles and inclusions. Glass containers are then fabricated from thehomogenized and refined glass melt. For example, in a standardcontainer-forming process, the glass melt is cooled in a forehearthchannel to around 1150° C. and then distributed as individual gobs ofmolten glass to individual sections of an individual section formingmachine by way of a gob delivery system. The glass gobs are formed intocontainers by a press-and-blow, a blow-and-blow, or some other shapingtechnique, typically at a temperature in excess of 900° C., followed bycooling of the containers to preserve their shape. The manufacturedglass containers are then reheated and cooled at a controlled rate in anannealing lehr to remove internal stress points. Any of a variety ofcoatings may be applied to the surface of the glass container eitherbefore (hot-end coatings) or after (cold-end coatings) annealing.

The inclusion of Na₂O and CaO in the chemistry of soda-lime-silica glassrenders the commercial manufacture of glass containers more practicaland less energy intensive while still yielding acceptable glassproperties. The Na₂O component functions as as a fluxing agent thatreduces the melting, softening, and glass transition temperatures of theglass, as compared to pure silica glass, and the CaO component functionsas a stabilizer that improves certain physical and chemical propertiesof the glass including its hardness and chemical resistance (especiallywith respect to water). Another oxide material, Al₂O₃, is commonly usedin the glass container manufacturing industry to improve the chemicaldurability of the glass. But the use of Na₂O, CaO, and other oxidematerials along with the primary network former, SiO₂, has to bebalanced against the susceptibility to devitrification, or thespontaneous growth of crystals such as devitrite (Na₂Ca₃Si₆O₁₆) on theglass surface, since the dilution of SiO₂ with network modifiers confersmobility within the glass oxide network, thus making it easier formolecular network chains to rearrange themselves into crystalstructures.

Devitrification is generally undesirable during the manufacture ofsoda-lime-silica glass containers because it reduces the transparencyand mechanical strength of the glass. Devitrification may occur insoda-lime-silica glass when the glass is held in a viscous supercooledliquid state at a temperature between its glass transition and liquidustemperatures for too long. And, as previously noted, the inclusion ofnetwork modifiers in the soda-lime-silica glass chemistry, in particularCaO, increases the susceptibility of the glass to devitrification byincreasing the liquidus temperature of the glass and enhancing networkchain mobility. The 1:1:6 molar ratio of Na₂O:CaO:SiO₂ insoda-lime-silica glass strikes the appropriate balance between energyconsumption, the physical and chemical properties of the glass, and theability to cool the containers relatively quickly through a viscoussupercooled liquid state to a temperature below the glass transitiontemperature while avoiding devitrification.

Glass-ceramics are a different class of materials than amorphous glassessuch as conventional soda-lime-silica glass. Unlike soda-lime-silicaglass, in which devitrification is purposefully avoided, glass ceramicsare formed by crystallizing or ceramizing a parent glass in a controlledmanner to form a crystalline phase distributed within an amorphousresidual glass phase. More specifically, in standard practices, a parentglass having a chemistry tailored to glass-ceramic processing is formed,usually by melt processing, and then heat-treated in a multi-stepprocedure to induce bulk internal nucleation followed by crystal growth.The bulk nucleation stage of the heat-treatment procedure induces nucleiseed formation homogeneously throughout the bulk of the parent glass,and the subsequent crystal growth stage, which may be conducted at ahigher temperature, grows crystals from and around those seeds. As such,the crystals in glass-ceramics are homogeneously distributed within theamorphous residual glass phase, as opposed to being formed andconcentrated on the glass surface as a result of the spontaneous andunwanted nucleation that typifies devitrification.

A wide variety of parent glass chemistries that are conducive toglass-ceramic manufacture are known. Some fairly common parent glasscompositions that have gained widespread applications are simplesilicates such as the Li₂O—SiO₂ system and aluminosilicates such as theLi₂O—Al₂O₃—SiO₂, MgO—Al₂O₃—SiO₂, and ZnO—Al₂O₃—SiO₂ systems. These andother parent glass compositions usually include nucleation agents thatpromote bulk nucleation via the formation of nuclei seeds throughout theparent glass. Examples of suitable nucleation agents include metals suchas gold, silver, platinum, palladium, and titanium, and nonmetals suchas fluorides, ZrO₂, TiO₂, P₂O₅, Cr₂O₃, and Fe₂O₃. As a result of theformation of a crystalline phase comprised of well-distributedfine-grain crystals, glass-ceramics tend to have higher strength,toughness, chemical durability, and electrical resistance than theirnoncrystallized parent glass, and also exhibit a relatively lowcoefficient of thermal expansion, which provides them with excellentthermal shock resistance.

Due to their unique and customizable properties, glass-ceramics havefound a wide variety of applications including aerospace and militaryproducts, cookware, satellite and telescope optics, dental restorations,and as bioactive materials. The glass container manufacturing industrymay also benefit from identifying glass-ceramics that can meet its needsfor various types of standard and specialty containers. It has beendetermined that a glass-ceramic based primarily on the sameNa₂O—CaO—SiO₂ ternary oxide system as conventional soda-lime-silicaglass-albeit one in which the chemistry is more conducive to controlledcrystallization-could potentially be a welcome addition to the glassmanufacturing art. Techniques for manufacturing such a glass-ceramichave also been identified that consume less energy than customarypractices of glass-ceramic manufacturing in which a parent glass isfirst produced at relatively high temperatures through melt processing.

SUMMARY OF THE DISCLOSURE

The present disclosure describes a glass-ceramic article, such as acontainer or a partially-formed container, and a method of forming thearticle from a chemically-synthesized feedstock gel comprising a baseoxide network that includes Na₂O, CaO, and SiO₂, with a molar ratio ofNa₂O:CaO:SiO₂ in the gel being 1:2:3 (i.e., Na₂O-2CaO-3SiO₂). Theglass-ceramic article is composed of a glass-ceramic material having anamorphous phase and a crystalline phase distributed within the amorphousphase, and the overall composition of the glass-ceramic materialcomprises the same Na₂O:CaO:SiO₂ molar ratio as its predecessorfeedstock gel, although the amorphous residual glass and crystallinephases may differ from one another at least in terms of their chemicalcontent. The feedstock gel may be synthesized at a low temperature froma liquid precursor medium that includes a reactive silicon-containingprecursor compound such as sodium silicate or a polysiloxane. Forexample, the liquid precursor medium may be an aqueous silicate solutionthat includes sodium silicate, or it may be an acidic aqueous solutionthat includes an alkoxysilanol as produced by the hydrolyticpolycondensation of a tetraalkoxysilane.

The “1:2:3” molar ratio of Na₂O:CaO:SiO₂ as used herein does not requirestrict adherence to a mathematically precise ratio of 1:2:3 but, rather,some fluctuation in the molar proportions of Na₂O, CaO, and SiO₂ ispermitted so long as the 1:2:3 molar ratio is maintained when roundingto a single significant digit. To be sure, in many instances, the 1:2:3molar ratio of Na₂O:CaO:SiO₂ is satisfied when the feedstock gel and theglass-ceramic material includes 15 mol % to 19 mol % Na₂O, 31 mol % to35 mol % CaO, and 48 mol % to 52 mol % SiO₂, based on the total amountof Na₂O, CaO, SiO₂ only, such that other materials that may be presentdo not affect the individual mole percentages. Compared to conventionalsoda-lime-silica glass, the glass-ceramic material described in thepresent disclosure has appreciably more CaO and appreciably less SiO₂.The resulting crystal phase in the glass-ceramic material includescombeite, rather than devitrite, wollastonite, or silica, which are thetypical crystal phases that result from crystalization ofsoda-lime-silica glass having an approximate 1:1:6 molar ratio ofNa₂O:CaO:SiO₂. Compared to the typical crystal phases, combeite is moreamenable to, and thus facilitates, bulk nucleation and crystal growthwithin the feedstock gel as the gel is converted into the glass-ceramicmaterial and shaped.

The present disclosure embodies a number of aspects that can beimplemented separately from or in combination with each other tosynthesize the feedstock gel and ultimately convert the gel into aglass-ceramic article such as a container (e.g., a bottle, jar, jug), apartially-formed container (e.g., a parison), a bowl, plate or othertableware, or any other suitable glass-ceramic article. According to oneaspect of the present disclosure, a method of making a glass-ceramicarticle includes synthesizing a feedstock gel that includes a base oxidenetwork comprising Na₂O, CaO, and SiO₂, with a molar ratio ofNa₂O:CaO:SiO₂ in the gel being 1:2:3. The feedstock gel is then pressedinto a compressed solid green-body and sintered at a temperature below900° C. to produce a solid monolithic body of a glass-ceramic materialthat has an amorphous phase and a crystalline phase distributed withinthe amorphous phase. The solid monolithic body of a glass-ceramicmaterial has a density that is greater than a density of the feedstockgel. Next, the solid monolithic body of a glass-ceramic material isdeformed into a glass-ceramic preform having a container shape. Theglass-ceramic preform is then cooled into a glass-ceramic article in theform of a container or a partially-formed container.

According to another aspect of the present disclosure, a method ofmaking a glass-ceramic article includes providing a liquid precursormedium that includes a reactive silicon-containing precursor compound.At least one soluble salt is added to the liquid precursor medium and aprecipitate is formed that comprises Na₂O, CaO, and SiO₂ in which amolar ratio of Na₂O:CaO:SiO₂ is 1:2:3. The at least one soluble salt isa soluble sodium salt, a soluble calcium salt, or both a soluble sodiumsalt and a soluble calcium salt. Next, the precipitate is dried into afeedstock gel that has a molar ratio of Na₂O:CaO:SiO₂ in the gel that isthe same as that of the precipitate (i.e., 1:2:3). The feedstock gel isthen converted into a glass-ceramic article at a temperature that doesnot exceed 900° C.

According to yet another aspect of the present disclosure, aglass-ceramic container comprises a main body having a bottom wall, anupstanding side wall extending from a periphery of the bottom wall, anda neck portion extending from the side wall opposite the bottom wall.The neck portion defines an opening to an internal containment spacedefined by the main body. The hollow main body is comprised of aglass-ceramic material that has an amorphous residual glass phase and acrystalline phase distributed within the amorphous residual glass phase.The glass-ceramic material, moreover, has a molar ratio of Na₂O:CaO:SiO₂that is 1:2:3. The glass-ceramic container may be formed from afeedstock gel by first sintering a compressed solid green-body of thefeedstock gel and then deforming the resultant solid monolithic body ofa glass-ceramic material into a container shape or, alternatively, theglass-ceramic container may be formed from the feedstock gel in someother manner.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure, together with additional objects, features, advantages,and aspects thereof, will be best understood from the followingdescription, the appended claims, and the accompanying drawings, inwhich:

FIG. 1 is a perspective view of a glass-ceramic article in the form of acontainer according to one embodiment of the disclosure;

FIG. 2 is a cross-sectional view of the glass-ceramic container shown inFIG. 1 taken along section line 2-2;

FIG. 3 is flowchart of a method of making the glass-ceramic containerthat generally includes a feedstock gel synthesis step and a feedstockgel conversion step;

FIG. 4 is a flowchart of the feedstock gel synthesis step depicted inFIG. 3 according to one embodiment of the disclosure;

FIG. 5 is a flowchart of the feedstock gel synthesis step depicted inFIG. 3 according to another embodiment of the disclosure;

FIG. 6A is a side cross-sectional view of generic die pressing apparatusshowing the feedstock gel loaded into a die cavity prior to beingpressed by a retractable piston rod into a compressed solid green-bodyaccording to one embodiment of the disclosure;

FIG. 6B is a side cross-sectional view of the generic die pressingapparatus showing the feedstock gel being pressed by the piston rod intothe compressed solid green-body according to one embodiment of thedisclosure;

FIG. 6C is a side cross-sectional view of the generic die pressingapparatus showing the compressed solid green-body of the feedstock gelfollowing retraction of the piston rod according to one embodiment ofthe disclosure;

FIG. 7A is a side cross-sectional view of a generic hot-stampingapparatus showing the solid monolithic glass-ceramic body loaded into amold cavity prior to being mechanically deformed by a retractableplunger into a glass-ceramic preform having a container shape accordingto one embodiment of the disclosure;

FIG. 7B is a side cross-sectional view of the generic hot-stampingapparatus showing the solid monolithic glass-ceramic body beingmechanically deformed by the plunger into the glass-ceramic preformaccording to one embodiment of the disclosure;

FIG. 7C is a side cross-sectional view of the generic hot-stampingapparatus showing the glass-ceramic preform following retraction of theplunger according to one embodiment of the disclosure; and

FIG. 8 a representative broken away perspective view of theglass-ceramic preform being cooled into a glass-ceramic article in theform of a glass-ceramic container according to practices of the methodset forth in the present disclosure.

DETAILED DESCRIPTION

A glass-ceramic container 10 constructed as ajar is shown in FIGS. 1-2as an example of a glass-ceramic article according to the presentdisclosure. The glass-ceramic container 10 includes a hollow main body12 that includes a bottom wall 12 a, an upstanding side wall 12 b thatextends upwards from a periphery of the bottom wall 12 a along a centralcontainer axis 14, and a neck portion 12 c that extends from theupstanding side wall 12 b and defines an opening 16 to the container 10.The opening 16 provides access to an internal containment space 18defined by the main body 12 for the storage of any of a wide variety ofmaterials including various solids and liquids. The neck portion 12 cmay also include a neck finish having a neck bead 20 and at least oneexterior surface feature 22 that enables a closure member (not shown) tobe attached and secured to the container 10. The surface feature 22shown here is a protruding helical thread disposed on and around theexterior surface of the neck portion 12 c, but the feature can be of anyother type which would allow the attachment of a closure.

The main body 12 is composed of a glass-ceramic material that has anamorphous residual glass phase and a crystalline phase distributedwithin the amorphous residual glass phase. The amorphous residual glassphase is a glass matrix that contains a disordered and spatiallycrosslinked ternary oxide network in much the same way asnon-crystalline glass. The crystalline phase is comprised of combeitecrystals, or Na₂Ca₂Si₃O₉, distributed homogeneously within the bulk ofthe amorphous residual glass phase. On a volume percent basis, theamorphous residual glass phase and the crystalline phase may constitutebetween 5% and 70% and between 30% and 95%, respectively, of theglass-ceramic material. And, in terms of its compositional make-up, theglass-ceramic material is based on the same primary oxides asconventional soda-lime-silica glass. Specifically, the glass-ceramicmaterial has an overall composition that comprises Na₂O, CaO, and SiO₂with a molar ratio of Na₂O:CaO:SiO₂ being 1:2:3. This higher sodium andcalcium content promotes bulk crystallization of the combeite crystals,so that crystallization is easier to initiate and control duringmanufacture of the glass-ceramic material, compared to conventionalsoda-lime-silica glass, which has a a molar ratio of Na₂O:CaO:SiO₂ thatis approximately 1:1:6.

While the overall composition of the glass-ceramic material has aNa₂O:CaO:SiO₂ molar ratio of 1:2:3, the compositions of the amorphousresidual glass phase and the crystalline phase, which togethercontribute to the overall composition, are not necessarily the same aseach other and the overall composition in terms of their Na, Ca, and Sicontent. Indeed, the combeite that forms upon crystallization has atendency to sequester a higher amount of Na₂O in the crystal thanstoichiometry would dictate. For example, in some embodiments, sodiumcations are sequestered in the combeite, thus leading to the crystallinephase of the glass-ceramic material having a higher sodium content thanthe amorphous residual glass phase. In such circumstances, the sodiumcontent in the crystalline phase may range from 12 at % to 16 at % whilethe sodium content in the amorphous residual glass phase may range 8 at% to 14 at %. In addition to the enhancements in strength, toughness,chemical durability, electrical resistance, and shock resistance thatare attributed to presence of the crystalline phase generally, asodium-enriched crystalline phase in the present glass-ceramic materialcan sequester ions that would otherwise leach out of the glass, therebyfurther enhancing chemical durability of the finished glass article.

The glass-ceramic container 10 is formed from a chemically-synthesizedfeedstock gel that is converted into the glass-ceramic container 10 at atemperature that does not exceed 900° C. The feedstock gel is agelatinous material that includes a base oxide network component and anextending swelling agent entrapped within the base oxide network. Thebase oxide network comprises a homogeneous chemical mixture of Na₂O,CaO, and SiO₂ with a molar ratio of Na₂O:CaO:SiO₂ being 1:2:3 (i.e.,Na₂O-2CaO-3SiO₂). The extending swelling agent is preferably water dueto the hydroscopic nature of the base oxide network component and theability of water to be physically and/or chemically entrained within theoxide network. The feedstock gel is light and has a high surface area.For instance, in a preferred embodiment, the feedstock gel has a densityof less than 2.0 g/cm³, preferably between about 1.0 g/cm³ and about 1.5g/cm³, including all ranges, sub-ranges, and values therebetween, and asurface area of at least 10 m²/g, preferably between 5 m²/g and 50 m²/g,including all ranges, sub-ranges, and values therebetween, as measuredby nitrogen BET adsorption.

The base oxide network component of the feedstock gel may optionallyinclude other material besides Na₂O, CaO, and SiO₂. Some examples ofsecondary materials that may also be homogeneously distributed withinthe base oxide network include colorants, decolorants, redox agents, orother agents that affect the physical and/or chemical properties thefinal glass-ceramic material of the glass-ceramic container 10. Specificcolorants and decolorants that may be present include the elementalforms or oxide compound forms of one or more of selenium, chromium,manganese, iron, cobalt, nickel, copper, niobium, molybdenum, silver,cadmium, indium, tin, gold, cerium, praseodymium, neodymium, europium,gadolinium, erbium, and uranium. And specific materials that can affectthe redox state and/or the physical properties of the glass-ceramicmaterial include one or more of carbon (up to 3 mol %), nitrates (up to3 mol %), selenium (up to 1 mol %), titanium oxide (TiO₂) (up to 5 mol%), arsenic oxide (As₂O₃) (up to 2 mol %), vanadium oxide (V₂O₅) (up to5 mol %), fluorines (up to 2 mol %), chlorines (up to 2 mol %), andsulfates (up to 2 mol %). A few examples of commonly used oxidizers andreducers include calcium sulfate (CaSO₄), sodium nitrate (NaNO₃),potassium nitrate (KNO₃), iron pyrite (FeS₂), and graphite.

Referring now to FIG. 3, a method 30 of making the glass-ceramiccontainer 10 generally includes a feedstock gel synthesis step 32 and afeedstock gel conversion step 34. There are different ways forperforming each of these steps 32, 34 including the various preferredtechniques described below with respect to FIGS. 4-8. The entire processfor forming the glass-ceramic container 10 can be performed relativelyquickly at modest temperatures compared to a other manufacturingpractices in which a glass melt obtained from heating a feedstock batchof virgin raw materials and optionally recycled glass at hightemperatures for long periods of time (e.g., greater than 1200° C. for24 hours or longer) is thermally conditioned and formed into a containerby standard glass forming techniques, followed by heat-treating thecontainer to induce the bulk internal nucleation and crystal growthneeded to convert the glass container into a glass-ceramic. Thus, inpracticing the disclosed method, less energy is consumed on a percontainer basis compared to processes that include some form of meltprocessing.

The feedstock gel synthesis step 32 involves chemically synthesizing thefeedstock gel from a liquid precursor medium. In general, this step 32involves providing the liquid precursor medium, in step 32 a, whichincludes a reactive silicon-containing precursor compound dissolved ordispersed in a solvent. Next, in step 32 b, at least one soluble salt isadded to the liquid precursor medium and a precipitate is formed fromthe liquid precursor medium that comprises Na₂O, CaO, and SiO₂ in the1:2:3 molar ratio of Na₂O:CaO:SiO₂ that is desired in the feedstock geland ultimately the glass-ceramic material of the glass-ceramic container10 or other article. The soluble salt added to the liquid precursormedium in step 32 b is selected from a soluble sodium salt, a solublecalcium salt, or both a soluble sodium salt and a soluble calcium salt.Finally, in step 32 c, excess liquid solvent is extracted from theprecipitate to produce the feedstock gel. Several implementations of thefeedstock gel synthesis step 32 using different reactivesilicon-containing precursor compounds are depicted in FIGS. 4-5. Otherprocedures not specifically described here may of course be employed tochemically synthesize the feedstock gel.

Referring now specifically to FIG. 4, the feedstock gel synthesis step32 may be carried out using a liquid precursor medium that includessodium silicate as the reactive silicon-containing precursor compound.In this regard, the liquid precursor medium provided in step 32 a may bean aqueous solution of sodium silicate, Na₂O.xSiO_(2(aq)), in which amolar ratio of Na₂O:SiO₂ (i.e, “x” in the chemical formulaNa₂O.xSiO_(2(aq))) within the sodium silicate may range from 1 to 3.75,including all ranges and sub-ranges therebetween, with a preferred molarratio of Na₂O:SiO₂ being one. The aqueous solution of sodium silicate ispreferably, but not necessarily, concentrated in that it contains atleast 5 wt % sodium silicate and, more preferably, between 25 wt % and40 wt % sodium silicate, in order to mitigate the loss of Na₂O and tohelp ensure that good ion exchange efficiency between Ca²⁺ and Na⁺ isrealized in the following step (step 32 b).

An aqueous solution of sodium silicate may be purchased commercially or,alternatively, it can be prepared, for example, by hydrothermallydissolving quartz sand in a caustic aqueous sodium-based solvent such assodium hydroxide (NaOH) concentrated to greater than 10 wt % (of thesodium base) a temperature between 25° C. and 300° C. and a pressurebetween 10 atm to 100 atm for a period of 3 hours to 24 hours. And,regardless of whether the sodium silicate solution is purchased orprepared, an acid such as nitric acid (HNO₃) may be added to thesolution to downwardly adjust the the molar ratio of Na₂O to SiO₂, ifdesired, to a lower number by neutralizing some of the Na₂O into silicicacid (SiH₄O₄) and sodium nitrate (NaNO₃). Any additional secondarymaterials that are desired in the feedstock gel may be added to thesolution at this time either as a solid or dissolved in water.

After the aqueous solution of sodium silicate has been provided in step32 a, a soluble calcium salt is added to the solution in step 32 b toform a precipitate having a molar ratio of Na₂O:CaO:SiO₂ that is 1:2:3,which is equal to the molar ratio Na₂O:CaO:SiO₂ desired in the baseoxide network of the feedstock gel. The soluble calcium salt ispreferably at least one of calcium nitrate (Ca(NO₃)₂) or calciumchloride (CaCl₂), although other calcium salts that can be a source ofcalcium cations may also be used. The introduction of the solublecalcium salt into the aqueous solution of sodium silicate reduces theNa₂O:SiO₂ molar ratio of the dissolved sodium silicate since sodiumcations are readily displaced with calcium ions. Such an ion exchangemechanism introduces calcium oxide into the sodium silicate and causesthe newly-modified silicate to precipitate out of solution. And sinceone mole of calcium ions (which results in a corresponding mole of CaO)displaces one mole of Na₂O in the dissolved sodium silicate, asexhibited in the representative chemical equation below, the amount ofthe soluble calcium salt that needs to be added into solution to providethe precipitate with the 1:2:3 molar ratio of Na₂O:CaO:SiO₂ can beeasily calculated based on the molar ratio of Na₂O:SiO₂ in the aqueoussolution of sodium silicate originally provided in step 32 a.1Na₂O.1SiO_(2(aq))+⅔Ca(NO₃)_(2(aq))→⅓Na₂O.⅔CaO.1SiO_(2(s))+⅔NaNO_(3(aq))

Next, in step 32 c, excess water is extracted from the precipitate toproduce the feedstock gel. The extraction of excess, non-entrained waterfrom the precipitate can be achieved by a number of techniques. Forinstance, water may first be separated from the precipitate throughcentrifugation, membrane osmosis, filter pressing, screw pressing,chemical separation, and/or mechanical compounding (e.g., squeezing).The remaining wet solids—which have been chemically synthesized in steps32 a and 32 b to have the desired formulation of Na₂O, CaO, and SiO₂—maythen be dried. Drying can be performed in a convection oven at moderatetemperatures ranging, for example, from 100° C. to 250° C. for a periodof 20 minutes to 120 minutes, or it can be performed in any othersuitable manner at conditions sufficient to remove residual water fromthe recovered solids. Rinsing of the recovered solids between initialwater separation and drying may optionally be performed to wash away anyreactants and/or reaction byproducts. When the water has beensatisfactorily removed, the feedstock gel remains, and at this point thegel is ready to be converted into the glass-ceramic container 10 or someother glass-ceramic article by way of the feedstock gel conversion step34.

The feedstock gel synthesis step 32 may also be carried out, as depictedin FIG. 5, using a liquid precursor medium that includes a polysiloxaneas the reactive silicon-containing precursor compound. In particular,the liquid precursor medium provided in step 32 a may be an acidicaqueous solution that includes a polysiloxane. A polysiloxane is apolymer that includes a siloxane backbone comprised of oxygen-bridgedsilicon atoms (—O—Si—O—) as well as leaving groups bonded to the siliconatoms. A variety of repeating functional groups may be linked to thesilicon atoms as the leaving groups. For example, in a preferredembodiment, the polysiloxane may be an alkoxysilanol. An alkoxysilanolis a polymer that includes a siloxane backbone and that further includesalkoxy (—OR) and hydroxyl (—OH) groups linked to the siloxane backbone.Each of the alkoxy and hydroxyl groups can be displaced by sodium andcalcium cations under the acidic conditions of the aqueous solutionwhile hydrolysis and polycondensation reactions are occurring.

An acidic aqueous solution that includes an alkoxysilanol may beprepared by providing an aqueous solution that includes an acidcatalyst, such as a 0.1-1M nitric acid (HNO₃) solution, followed byadding a tetraalkoxysilane to the aqueous solution while agitating(e.g., stirring) the solution. Other acid catalysts such as acetic acidor hydrchloric acid may be used as well. The tetraalkoxysilane added tothe acidic solution is preferably tetraethyl orthosilicate (TEOS),tetramethyl orthosilicate (TMOS), or a mixture thereof, although othertetraalkoxysilanes may certainly be used. Upon being added to theaqueous solution that includes an acid catalyst, the tetraalkoxysilaneundergoes hydrolytic polycondensation in which alkoxy functional groupsare first substituted with hydroxyl functional groups followed bycondensation reactions to produce the siloxane backbone of thealkoxysilanol. When, for example, TEOS is added to the acidic solution,the alkoxysilanol may be an ethoxysilanol in the sense that ethoxyfunctional groups (—OC₂H₅) and hydroxyl functional groups are linked tothe siloxane backbone. Similarly, when TMOS is added to the acidicsolution, the alkoxysilanol may be a methoxysilanol in the sense thatmethoxy functional groups (—OCH₃) and hydroxyl functional groups arelinked to the siloxane backbone.

After the aqueous solution that includes a polysiloxane, or morepreferably an alkoxysilanol, has been provided in step 32 a, a solublesodium salt and a soluble calcium salt are added to the solution in step32 b to introduce sodium and calcium, respectively, into thealkoxysilanol. The soluble sodium salt is preferably at least one ofsodium hydroxide (NaOH), sodium nitrate (Na(NO₃)), or sodium chloride(NaCl), and the soluble calcium salt is preferably at least one ofcalcium nitrate (Ca(NO₃)₂) or calcium chloride (CaCl₂), although othersodium and calcium salts that can be a source of sodium and calciumcations, respectively, may also be used. The soluble sodium and calciumsalts are preferably added to the aqueous polysiloxane solutionsequentially while agitating the solution; that is, all of the solublesodium salt is added first and then all of the soluble calcium salt isadded next, or vice versa. The addition of the soluble sodium andsoluble calcium salts to the aqueous polysiloxane solution displaces thehydroxyl functional groups, causing precipitation that entraps Na⁺ andCa²⁺ ions. The resultant precipitate includes Na₂O and CaO in additionto SiO₂. The relative molar quantities of the soluble sodium and solublecalcium salts can be calculated and added to the aqueous polysiloxanesolution to provide the precipitate with a molar ratio of Na₂O:CaO:SiO₂that is 1:2:3, which is equal to the molar ratio of Na₂O:CaO:SiO₂desired in the base oxide network of the feedstock gel.

The precipitate is eventually collected by halting agitation of thesolution and allowing and/or assisting the precipitate and the supernateto separate over time at ambient conditions of atmospheric pressure and20° C.-25° C. The precipitate has a molar ratio of Na₂O:CaO:SiO₂ that is1:2:3. In that sense, the precipitate obtained here from the liquidprecursor medium that includes a polysiloxane is essentially the same interms of its chemical composition as the precipitate obtained from theliquid precursor medium that includes sodium silicate, with theexception that some byproducts and excess residual solvent contained inthe precipitate may be different. Consequently, in light of thesesimilarities, excess water may be extracted from the precipitate in thisembodiment to produce the feedstock gel in step 32 c in the same manneras described above—including the initial separation of water followed bydrying along with optional rinsing of the recovered solids—inanticipation of the feedstock gel conversion step 34.

After being synthesized, the feedstock gel is converted into theglass-ceramic container 10, or some other glass-ceramic article, in thefeedstock gel conversion step 34, which can be accomplished at atemperature that does not exceed 900° C. The feedstock gel conversionstep 34 may include a pressing step 34 a, a sintering step 34 b, adeforming step 34 c, and a cooling step 34 d, as depicted in FIG. 3. Theability to convert the feedstock gel into the glass-ceramic container 10at such temperatures by way of sintering and deformation, in combinationwith the fact that the feedstock gel is chemically synthesized, impartsgood energy efficiency to the overall method 30 since the hightemperatures and long heating times associated with conventional glassmelt processing can be avoided. What is more, the need to manage theflow and distribution of a corrosive glass melt, and intermediate glassprecursor melts, and to maintain equipment that can tolerate therelatively harsh environment that accompanies the handling of a glassmelt are generally not implicated in the disclosed method 30.

The pressing step 34 a is shown schematically in FIGS. 6A-6C andinvolves pressing the chemically-synthesized feedstock gel (identifiedhere by reference numeral 40) into a compressed solid green-body 42 in adie-pressing apparatus 44. To begin, the feedstock gel 40 is loaded intoin a die cavity 46 of the apparatus 44, as shown in FIG. 6A. The diecavity 46 here has a cylindrical cross-sectional shape. Once thefeedstock gel 40 is in place, as shown in FIG. 6A, a retractable pistonrod 48 having a piston head 50 is inserted into the die cavity 46 suchthat the piston head 50 slidingly mates with the side walls that definethe die cavity 46. The retractable piston rod 48 is advanced within thedie cavity 46 to bring a front surface 52 of the piston head 50 intopressed engagement with the feedstock gel 40. The piston head 50 ispressed against the feedstock gel 40 at an applied downward pressure of,preferably, 25 MPa to 100 MPa for a time of 30 seconds to 5 minutesusing a hydraulic actuator 54. The compressive force applied by thepiston head 50 compacts the feedstock gel 40 into the compressed solidgreen-body 42, as shown in FIG. 6B, where the gel material is heldtogether in a weak, yet portable, physically consolidated disc-shapedmass. After the requisite compression has been achieved, the piston rod48 is retracted to separate the front surface 52 of the piston head 50from the compressed solid green-body 42, as shown in FIG. 6C, and thegreen-body 42 is removed from the die-pressing apparatus 44.

The compressed solid green-body 42 of the feedstock gel is then sinteredinto a solid monolithic body of a glass-ceramic material 56 (FIG. 7A) ofapproximately the same disc shape in the sintering step 34 b. To producethe solid monolithic glass-ceramic body 56, the sintering processincludes heating the compressed solid green-body 42 to fuse thegreen-body 42 together by way of a solid-state particle softening anddiffusion mechanism without melting the gel to the point ofliquification while at the same time inducing bulk crystallization ofthe fusing mass (i.e., sinter-crystallization). Crystallization of thesintered glass material can readily occur during the sintering step 34 bbecause the composition of the base oxide network of the feedstock geland, in particular, the molar ratio of Na₂O:CaO:SiO₂, allows for enoughmobility of the molecular network chains at sintering temperatures thatthe chains can rearrange themselves into combeite crystal structureshaving repeating structural units. As such, the solid monolithicglass-ceramic body 56 that results from the sintering step 34 b isunitary block of a heated glass-ceramic material that includes both theamorphous residual glass phase and the crystalline phase of combeite, asdescribed above, although the final proportions of those two phases involume percent may not yet be finally established. The solid monolithicglass-ceramic body 56 has a density that is greater than the density ofthe feedstock gel 40 due to the densification that occurs during thesintering step 34 b.

The compressed solid green-body 42 of the feedstock gel may be sinteredat a temperature between 600° C. and 900° C. and held at thattemperature for a period of time to carry out the sintering step 34 b.For example, in a preferred embodiment, the compressed solid green-body42 may be heated until it reaches a sintering temperature between 600°C. to 900° C. or, more narrowly, between 680° C. to 750° C., at whichpoint the green-body 42 (a term which includes any transition phasebetween the green-body 42 and solid monolithic glass-ceramic body 56)may be held at the sintering temperature for a period of 1 minute to 30minutes. The sintering step 34 b may be preceded by an optionalpreheating step 34 e in order to burn off any binder material or solventthat may have been used to aid in the compaction and retention of thethe green-body 42 of the feedstock gel, as well as other foreigncontaminate matter that may be present. This optional preheating step 34e may involve initially heating the compressed solid green-body 42 to aburn-off temperature between 100° C. to 400° C. and holding thegreen-body 42 at that temperature for a period of 5 minutes to 60minutes and, thereafter, continuing to heat the compressed solidgreen-body 40 up to the sintering temperature. The heating that typifiesthe sintering step 34 b may be conducted in a belt-type furnace or oven,such as a lehr, to facilitate more efficient manufacturing cycle times,although other heating techniques and apparatuses may certainly beemployed.

The solid monolithic glass-ceramic body 56 produced in the sinteringstep 34 b is then deformed mechanically into a glass-ceramic preform(identified by reference numeral 58 (FIGS. 7B-7C)) in the deformationstep 34 c at a temperature of 680° C. or above. The mechanicaldeformation step 34 c may include hot-pressing the solid monolithicglass-ceramic body 56 into the glass-ceramic preform 58 in ahot-stamping apparatus 60. In this regard, as shown in FIG. 7A, thesolid monolithic glass-ceramic body 56 is transferred into a mold cavity62 of the hot-stamping apparatus 60 while still at an elevatedtemperature at or above 680° C. as a result of being heated during thesintering step 34 b. The mold cavity 62, as shown, may be defined by aconvex surface 64 of a bottom plate 66 and an upstanding peripheralsurface 68 of a side wall 70 that is affixed to and surrounds acircumference of the bottom plate 66. The side wall 70 may additionallybe outfitted with a neck ring 72 having at least one intrusion 74 suchas, for example, a continuous helical groove or other feature that canbe used to attach a closure to the container. The neck ring 72 may beinstalled in the side wall 70 to provide the peripheral surface 68 withthe profile needed to create a neck finish on the exterior of the neckportion 12 c of the glass-ceramic container 10.

Once the solid monolithic glass-ceramic body 56 is located in the moldcavity 62, a retractable plunger or mandrel 76 is inserted into the moldcavity 62 while being centrally guided by a guide ring 78 locatedadjacent to the opening of the mold cavity 62 within the side wall 70.The plunger 76 is advanced against the solid monolithic glass-ceramicbody 56 within the mold cavity 62 to force the glass-ceramic body 56 todeform up and around the plunger 76 so as to occupy the available spacebetween the plunger 76 and the upstanding peripheral surface 68 of theside wall 70, as shown in FIG. 7B. To accomplish such mechanicaldeformation at an acceptable deformation rate, the plunger 76 may applya downward pressure against the solid monolithic glass-ceramic body 56of, preferably, 5 MPa to 25 MPa for a time period of 3 seconds to 30seconds while the bottom plate 66 and the side wall 70 of thehot-stamping apparatus 60 are maintained at a temperature between 600°C. and 750° C. The forcible downward pressure applied by the plunger 76may be delivered by a hydraulic actuator 80 that acts on the plunger 76through a ram extender 82. After the solid monolithic glass-ceramic body56 has been deformed into the glass-ceramic preform 58, the plunger 76is retracted, as shown in FIG. 7C, and the preform 58 is removed fromthe hot-stamping apparatus 60.

The glass-ceramic preform 58 is formed of the same glass-ceramicmaterial as the solid monolithic glass-ceramic body 56 and has acontainer shape. The container shape of the glass-ceramic preform 58 mayvary. For example, the container shape may resemble the shape of thefinal glass-ceramic container, such as the shape of the glass-ceramiccontainer 10 shown in FIGS. 1-2, or it can resemble the shape of apartially-formed container such as a parison that ultimately needs toundergo additional processing, such as blowing, to be transformed intothe final container shape. As such, and referring for the moment back toFIGS. 1-2 as a representative example, the “container shape” of theglass-ceramic preform 58 may resemble the size and shape of the hollowmain body 12 or it may resemble the size and shape of a hollow yetpartially-formed parison that can be later formed into the hollow mainbody 12, typically by expanding the parison with compressed air whilethe parison is at an elevated temperature similar to that used tomechanically deform the solid monolithic glass-ceramic body 56 into theglass-ceramic preform 58. If the container shape resembles a hollow yetpartially-formed parison, the glass-ceramic article produced from thepreform 58 upon cooling would, consequently, be a partially-formedcontainer.

The glass-ceramic preform 58 is shown in FIG. 8 for illustrativepurposes as representing the final shape of the glass-ceramic container10 and, thus, has a hollow main body 12′. The hollow main body 12′includes a bottom wall 12 a′, an upstanding side wall 12 b′, and a neckportion 12 c′, and further defines an internal containment space 18′ andan opening 16′ to the internal containment space 18′. The exact shapeand profile of the hollow main body 12′ is dictated by the contours ofthe mold cavity 62 of the hot-stamping apparatus 60. Indeed, in thespecific embodiment shown here in FIG. 8, the bottom wall 12 a′ is bowedinto the internal containment space 18′ in complimentary conformance tothe convex surface 64 of a bottom plate 66, and the upstanding side wall12 b′ extends upwardly from a periphery of the bottom wall 12 a′ to theneck portion 12 c′ in complimentary conformance to the upstandingperipheral surface 68 of the side wall 70 beneath the neck ring 72. Theneck portion 12 c′ is the distal portion of the hollow main body 12′ anddefines the opening 16′ to the internal containment space 18′. The neckportion 12 c′ may have a neck bead 20′ and at least one exterior surfacefeature 22′ that is shaped inversely to the at least one intrusion 74contained in the neck ring 72. For example, the at least one exteriorfeature 22′ of the neck portion 12 c′ may include a continuousprotruding exterior helical thread.

The hollow main body 12′ of the glass-ceramic preform 58 in thisembodiment shown in FIG. 8 is thus a three-dimensional container-shapedmonolithic structure of the glass-ceramic material whose temperature isstill above 600° C., but not higher than 900° C., as a result of thedeformation step 34 c. The container shape assumed by the glass-ceramicpreform 58 at this point is identical or nearly identical to the finalshape and profile of the glass-ceramic container 10 except for somemarginal thermal contraction that may occur during the cooling step 34 dand which generally cannot be visually detected by human eyesight.Further crystallization may or may not continue to occur within theglass-ceramic material while the glass-ceramic preform 58 is at anelevated temperature state. The container shape of the glass-ceramicpreform 58 may assume a wide variety of configurations associated withjars and bottles including, for example, beverage and food containers,and as explained above, may resemble the shape of the final container ora partially-formed container such as a parison.

The cooling step 34 d is performed after the formation of theglass-ceramic preform 58. During the cooling step 34 d, theglass-ceramic preform 58 is cooled from its elevated temperature intothe glass-ceramic container 10 while retaining thepreviously-established container shape. The cooling of the glass-ceramicpreform 58 into the glass-ceramic container 10 may involve cooling thepreform 58 at a controllable rate of 5° C./min to 50° C./min until itreaches room temperature (i.e., 20° C.-25° C.), although othertime-temperature cooling practices may be used. The resultantglass-ceramic container 10 has the chemical, electrical, optical, andmechanical properties typically associated with glass-ceramic materialsas compared to conventional amorphous soda-lime-silica glass materials.For instance, and as most relevant to containers, the glass-ceramiccontainer 10 exhibits good strength, toughness, and chemical durability,and also has the added benefit of a low coefficient of thermalexpansion.

There thus has been disclosed a glass-ceramic container and a method ofmaking a glass-ceramic container from a feedstock gel that satisfies oneor more of the objects and aims previously set forth. The disclosure hasbeen presented in conjunction with several illustrative embodiments, andadditional modifications and variations have been discussed. Othermodifications and variations readily will suggest themselves to personsof ordinary skill in the art in view of the foregoing discussion. Forexample, the subject matter of each of the embodiments is herebyincorporated by reference into each of the other embodiments, forexpedience. The disclosure is intended to embrace all such modificationsand variations as fall within the spirit and broad scope of the appendedclaims.

The invention claimed is:
 1. A method of making a glass-ceramic article,the method comprising: synthesizing a feedstock gel that includes a baseoxide network comprising Na₂O, CaO, and SiO₂ in which a molar ratio ofNa₂O:CaO:SiO₂ is 1:2:3; pressing the feedstock gel into a compressedsolid green-body; sintering the compressed solid green-body of thefeedstock gel at a temperature below 900° C. to produce a solidmonolithic body of a glass-ceramic material having an amorphous residualglass phase and a crystalline phase distributed within the amorphousresidual glass phase, the solid monolithic body of a glass-ceramicmaterial having a density that is greater than a density of thefeedstock gel; deforming the solid monolithic body of a glass-ceramicmaterial into a glass-ceramic preform having a container shape at atemperature of 600° C. or above; and cooling the glass-ceramic preforminto a hollow glass-ceramic article that retains the container shape. 2.The method set forth in claim 1, wherein the step of synthesizing thefeedstock gel comprises: providing an aqueous solution that includessodium silicate having a Na₂O:SiO₂ molar ratio; adding a soluble calciumsalt to the aqueous solution to form a precipitate having aNa₂O:CaO:SiO₂ molar ratio that corresponds to the molar ratio ofNa₂O:CaO:SiO₂ in the base oxide network of the feedstock gel; andextracting liquid solvent from the precipitate to produce the feedstockgel.
 3. The method set forth in claim 2, wherein the calcium saltcomprises at least one of calcium nitrate or calcium chloride.
 4. Themethod set forth in claim 1, wherein the step of synthesizing thefeedstock gel comprises: providing an aqueous solution that includes anacid catalyst; adding a tetraalkoxysilane to the aqueous solution toform a polysiloxane through hydrolytic polycondensation of thetetraalkoxysilane; adding a soluble sodium salt and a soluble calciumsalt to the aqueous solution to introduce sodium and calcium,respectively, into the polysiloxane; forming a precipitate that has aNa₂O:CaO:SiO₂ molar ratio that corresponds to the molar ratio ofNa₂O:CaO:SiO₂ in the base oxide network of the feedstock gel; andextracting liquid solvent from the precipitate to produce the feedstockgel.
 5. The method set forth in claim 4, wherein the tetraalkoxysilaneis tetraethyl orthosilicate, tetramethyl orthosilicate, or a mixturethereof.
 6. The method set forth in claim 4, wherein the acid catalystis nitric acid, acetic acid, or hydrochloric acid.
 7. The method setforth in claim 4, wherein the sodium salt comprises at least one ofsodium hydroxide, sodium nitrate, or sodium chloride, and wherein thecalcium salt comprises at least one of calcium nitrate or calciumchloride.
 8. The method set forth in claim 1, wherein the step ofsintering the feedstock gel into the solid monolithic body of aglass-ceramic material is performed at a temperature of 600° C. to 900°C.
 9. The method set forth in claim 1, wherein the step of deforming thesolid monolithic body of a glass-ceramic material into the glass-ceramicpreform is performed at a temperature between 600° C. and 750° C. 10.The method set forth in claim 9, wherein the step of deforming the solidmonolithic body of a glass-ceramic material into the glass-ceramicpreform comprises hot-pressing the monolithic body of a glass-ceramicmaterial in a mold cavity.
 11. The method set forth in claim 1, whereinthe glass-ceramic article is a container that comprises a hollow mainbody that defines an opening and an internal containment spaceaccessible through the opening.
 12. The method set forth in claim 1,wherein the glass-ceramic article is a glass-ceramic parison, andfurther comprising: blowing the glass-ceramic parison to expand theparison into a glass-ceramic container comprised of a hollow main bodythat has a bottom wall, an upstanding side wall extending from aperiphery of the bottom wall, and a neck portion extending from the sidewall opposite the bottom wall and defining an opening to an internalcontainment space defined by the hollow main body.
 13. A method ofmaking a glass-ceramic article, the method comprising: synthesizing afeedstock gel from a liquid precursor medium that includes a reactivesilicon-containing precursor compound, the feedstock gel including abase oxide network comprising Na₂O, CaO, and SiO₂ in which a molar ratioof Na₂O:CaO:SiO₂ is 1:2:3; pressing the feedstock gel into a compressedsolid green-body; sintering the compressed solid green-body of thefeedstock gel at a temperature below 900° C. to produce a solidmonolithic body of a glass-ceramic material having an amorphous residualglass phase and a crystalline phase distributed within the amorphousresidual glass phase; deforming the solid monolithic body of aglass-ceramic material into a glass-ceramic preform having a containershape at a temperature of 600° C. or above; and cooling theglass-ceramic preform into a glass-ceramic container comprised of ahollow main body that has a bottom wall, an upstanding side wallextending from a periphery of the bottom wall, and a neck portionextending from the side wall opposite the bottom wall and defining anopening to an internal containment space defined by the hollow mainbody.
 14. The method set forth in claim 13, wherein the liquid precursormedium is selected from an aqueous silicate solution that includessodium silicate or an acidic aqueous solution that includes analkoxysilane.
 15. The method set forth in claim 13, wherein deformingthe solid monolithic body of a glass-ceramic material compriseshot-pressing the solid monolithic body of a glass-ceramic material in amold cavity at a temperature between 600° C. to 750° C. to form theglass-ceramic preform having a container shape.
 16. A method of making aglass-ceramic article, the method comprising: synthesizing a feedstockgel that includes a base oxide network comprising Na₂O, CaO, and SiO₂ inwhich a molar ratio of Na₂O:CaO:SiO₂ is 1:2:3, wherein synthesizing thefeedstock gel comprises; providing a liquid precursor medium thatincludes a reactive silicon-containing precursor compound selected fromsodium silicate or a polysiloxane; adding at least one soluble salt tothe liquid precursor medium selected from a soluble sodium salt, asoluble calcium salt, or both a soluble sodium salt and a solublecalcium salt, wherein adding the at least one soluble salt causes aprecipitate to form that includes Na₂O, CaO, and SiO₂ in which a molarratio of Na₂O:CaO:SiO₂ in the precipitate is 1:2:3; and extractingliquid solvent from the precipitate to produce the feedstock gel;pressing the feedstock gel into a compressed solid green-body; sinteringthe compressed solid green-body of the feedstock gel at a temperaturebelow 900° C. to produce a solid monolithic body of a glass-ceramicmaterial having an amorphous residual glass phase and a crystallinephase distributed within the amorphous residual glass phase; deformingthe solid monolithic body of a glass-ceramic material into aglass-ceramic preform having a container shape at a temperature of 600°C. or above; and cooling the glass-ceramic preform into a glass-ceramicarticle in the form of a container or a parison.
 17. The method setforth in claim 16, wherein deforming the solid monolithic body of aglass-ceramic material comprises hot-pressing the solid monolithic bodyof a glass-ceramic material in a mold cavity at a temperature between600° C. and 750° C. to form the glass-ceramic preform having a containershape.
 18. The method set forth in claim 16, wherein the glass-ceramicarticle is a glass-ceramic container comprised of a hollow main bodythat has a bottom wall, an upstanding side wall extending from aperiphery of the bottom wall, and a neck portion extending from the sidewall opposite the bottom wall and defining an opening to an internalcontainment space defined by the hollow main body.
 19. A method ofmaking a glass-ceramic article, the method comprising: synthesizing afeedstock gel that includes a base oxide network comprising Na₂O, CaO,and SiO₂ in which a molar ratio of Na₂O:CaO:SiO₂ is 1:2:3; pressing thefeedstock gel into a compressed solid green-body; sintering thecompressed solid green-body of the feedstock gel at a temperature below900° C. to produce a solid monolithic body of a glass-ceramic materialhaving an amorphous residual glass phase and a crystalline phasedistributed within the amorphous residual glass phase; hot-pressing thesolid monolithic body of a glass-ceramic material in a mold cavity at atemperature between 600° C. and 750° C. to form a glass-ceramic preformhaving a container shape; and cooling the glass-ceramic preform into ahollow glass-ceramic article that retains the container shape.
 20. Themethod set forth in claim 19, wherein the glass-ceramic article is aglass-ceramic container comprised of a hollow main body that has abottom wall, an upstanding side wall extending from a periphery of thebottom wall, and a neck portion extending from the side wall oppositethe bottom wall and defining an opening to an internal containment spacedefined by the hollow main body.